Enzymes prostaglandins

Figure 23-6. Conversion of arachidonicacid to prostaglandins and thromboxanes of series 2. (PG, prostaglandin TX, thromboxane PGI, prostacyclin HHT, hydroxyheptadecatrienoate.) (Asterisk Both of these starred activities are attributed to one enzyme prostaglandin H synthase. Similar conversions occur in prostaglandins and thromboxanes of series 1 and 3.)...

Skelley et al (1973) listed a number of substances that may be determined quantitatively by the help of the RIA method, namely nucleic acids, proteins, enzymes, prostaglandins, steroidal hormones, antibodies, cancer and viral antigens, vitamins, and drugs together with their respective metabolites. 

The enzyme prostaglandin H2 synthase-1 (PGHS-1) manufactures prostaglandin H2, which is converted to prostaglandin E2 and causes fever and inflammation. PGHS-1 contains two protein subunits with long channels. 

Q Mechanism of Inhibits the enzyme prostaglandin cyclooxygenase in platelets, which... 

The thromboxanes have a six-membered ring containing an ether. They are produced by platelets (also called thrombocytes) and act in the formation of blood clots and the reduction of blood flow to the site of a clot. The nonsteroidal antiinflammatory drugs (NSAIDs)— aspirin, ibuprofen, and meclofenamate, for example— were shown by John Vane to inhibit the enzyme prostaglandin H2 synthase (also called cyclooxygenase or COX), which catalyzes an early step in the pathway from arachidonate to prostaglandins and thromboxanes (Fig. 10-18 see also Box 21-2). 

Prostaglandin A member of the family of 20-carbon fatty acid compounds (eicosanoids) formed from arachidonic acid by the cyclooxygenase enzyme. Prostaglandins help regulate normal cell activity, and may help mediate certain pathologic responses, including pain, inflammation, fever, and abnormal blood coagulation. 

Prostaglandins are mediators of the inflammatory response and are produced by the action of two activities of the enzyme prostaglandin synthase. The first activity is a cyclooxygenase activity, which adds two oxygen molecules the arachidonic acid. Secondly, the peroxide group from the first step is reduced to a hydroxyl group. 

Phagocytosis, granule release, lytic enzymes, prostaglandins... 

Prostaglandins are biosynthesized from arachidonic acid, an unsaturated fatty acid containing four double bonds. The enzyme prostaglandin endoperoxide synthase converts arachidonic acid to PGH2, which serves as the precursor for prostaglandins and related compounds. Aspirin exerts its pharmacological effect by inhibiting this enzyme. 

Phosphatidic acid phosphatase Post proline cleaving enzyme Prostaglandin dehydrogenase Succinate dehydrogenase Sulfotransferase... 

Kudo I, Murakami M. 2002. Phospholipase A2 enzymes. Prostaglandins Other Lipid Mediat 68-69 3-58. 

Radical production from peroxidase-like systems, for example from the peroxide-supported oxidation of amino compounds catalyzed by protohemin and metmyo-globin, has received attention [174]. Both hydrogen peroxide and hydroperoxides (e.g., r-butyl hydroperoxide and cumene hydroperoxide) can be effective sources of oxidizing equivalents for these reactions. Since the enzyme prostaglandin synthase contains both cyclooxygenase and hydroperoxidase activities, either a substrate for the cyclooxygenase or an added hydroperoxide will support the catalyzed oxidation of substrates [175]. 

Aspirin (acetylsalicylic acid) provides an example of a pharmacologic drag that exerts its effect throngh the covalent acetylation of an active site serine in the enzyme prostaglandin endoperoxide synthase (cycloxygenase). Aspirin resembles a portion of the prostaglandin precnrsor that is a physiologic substrate for the enzyme. 

Fig. 35.8. Formation of prostaglandins (including the prostacyclin PGIj) and thromboxane TXAj from arachidonic acid. The conversion of arachidonic acid to PGHj is catalyzed by a membrane-bound enzyme, prostaglandin endoperoxide synthase, which has cyclooxygenase and peroxidase activities. The reducing agent is glutathione (GSH), which is oxidized to GSSG.

Tai, HH, Ensor, CM, Tong, M, Zhou, H and Yan, F (2002) Prostaglandin catabolizing enzymes. Prostaglandins Other Lipid Mediat, 69, 483-493. 

Prostaglandins have several different physiological functions. One is to stimulate inflammation and another to induce fever. The enzyme prostaglandin synthase catalyzes the conversion of arachidonic acid into PGH2, a precursor of all prostaglandins and the related thromboxanes. 

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